A machine-readable code, such as a bar code, may be usefully employed in the automated high-speed processing of documents, such as, for example, the processing of checks in banks and other financial institutions. Bar codes are particularly well suited for use in connection with the processing of checks and similar documents, since they are easily printed, easily read by machine "on the fly," as the document is being transported, and can store a substantial amount of information in a relatively small space. Various types of bar codes are currently known, such as binary codes based upon the printing (=1) or nonprinting (=0) of a bar, the use of bars of different lengths and widths, and the use of bars of different colors. Since sorting and other mechanical document handling operations can be facilitated and enhanced by including various categories of information in that which is encoded and placed on the document, and since the amount of space for such coded information on the document is limited, the development of codes which increase the density of information storage can contribute substantially to increased efficiency in the automated processing of documents.